The present invention relates to apparatus for positioning sheet-like or strip-shaped commodities, such as sheet-like or strip-shaped originals in photographic copying machines. More particularly, the invention relates to improvements in replaceable or exchangeable apparatus for positioning such commodities on the table of a copier or the like.
Positioning apparatus as used in photographic copying machines to properly locate an original with reference to the plane of the image-receiving sheet as well as with reference to the light source and optical system of the copying machine. The arrangement is normally such that the original to be copied is inserted (e.g., by hand) between a platform which constitutes the lowermost component of the holder for originals and a hold-down device which, in turn, is overlapped by a cover. The latter is normally coupled to the platform so that it can be pivoted to and from a position in which it overlies the platform and the hold-down device. The purpose of the hold-down device and of the cover is to ensure that the original is held in requisite position, at least during the interval of exposure to copying light, so as to enable the machine to make sharp reproductions of one or more selected portions of or of the entire original. If the originals are introduced and removed by hand, the apparatus should be designed with a view to allow for rapid positioning of successive originals with a requisite degree of accuracy so as to ensure that little time will be wasted between the making of successive exposures.
In a presently known positioning apparatus which is manufactured and sold by the assignee of the present application and is used in a copying machine which can make larger or smaller reproductions, the hold-down device is installed at one side of the opening in the platform of the holder, namely, at that side which is nearest to the hinge or hinges between the platform and the cover. The hold-down device is formed with an elongated locating edge against which a portion of the original abuts when the original is properly positioned on the platform. Such apparatus are quite satisfactory if the originals are flat, i.e., if the originals do not exhibit any or do not exhibit a pronounced tendency to curl. However, exposed and developed photographic films which are supplied to the copying machine in the form of long strips consisting of a series of spliced-together customer films will curl as soon as allowed, i.e., in the absence of a force which holds them in a predetermined plane. Such tendency of photographic films to curl is not characteristic only of elongated strips, i.e., of webs each of which constitutes an entire customer film or a series of serially connected customer films, but also of relatively short film sections each of which consists of a few film frames as well as of individual film frame. Relatively short sections are formed preparatory to shipment of exposed and developed films back to the customers or to the dealers.
It has been found that, when a relatively short section of sheet-like or strip-shaped material is placed against the aforementioned locating edge of the hold-down device in a conventional positioning apparatus and the cover is thereupon placed over the hold-down device, the cover often shifts the inserted original with reference to the hold-down device so that the openings of the platform and cover are not in accurate register with a selected portion (e.g., a particular film frame) of the inserted original. Moreover, the insertion and proper positioning of curled originals into an apparatus of the above outlined character is rather time-consuming and difficult because, when an original overlies the opening of the platform, the outline of such opening cannot be readily seen through the original so that the person in charge must devote much attention to proper positioning of the original with reference to the platform and with reference to the hold-down device.